Drive guides are known to retain and drive fastening bits (such as screwdriving bits) using a power tool. As shown in FIGS. 16A-16D, in one prior art example, a DeWALT DW2055 Magnetic Drive Guide 10 comprises a drive shaft 12, a socket shaft 20, and a sliding sleeve 30. The drive shaft 12 has a hex-shaped rear shank portion 14 configured to be received in a driving end of an electric screwdriving tool, an intermediate shaft portion 15 with longitudinal grooves 18, and a round front shaft portion 16. The front shaft portion 16 is non-rotatably press fit in a bore (not shown) in a rear end 22 of the socket shaft 20. A hex shaped socket (not shown) for receiving a screwdriving bit 36 is formed in a front end 24 of the socket shaft. A magnet (not shown) may be received in the socket to retain and magnetize the screwdriving bit. Coupled to the socket shaft 30 are a rear hog ring 26 at the rear 22 end and a front hog ring 28 at the front end 24. The sliding sleeve 30 is received over the socket shaft 20. The sliding sleeve 30 is hollow and cylindrical with a V-shaped internal annular groove 32 at its rear end 34. The sleeve can slide between a rear position (FIG. 16A) where the rear hog ring 26 is received in the annular groove 32, and a front position (FIG. 16B) where the front hog ring is received in the annular groove. The drive shaft 12 is composed of mild steel, the socket shaft 20 is composed of aluminum, and the sliding sleeve 30 is composed of brass.
These prior art drive guides tend to fail frequently (e.g., approximately 50% of the time or more), especially when used with an impact driver. The usual points of failure are the rear hog ring becoming jammed in the V-shaped annular groove in the sliding sleeve and the socket in the front of the socket shaft fracturing or becoming worn. After use in an impact driver, the sliding sleeve can be difficult to slide between the rearward and forward positions and tends to get stuck in one of these positions. Finally, regardless of whether the drive guide is used in an impact driver, some of the magnetism from the magnet tends to magnetize the drive shaft, which reduces the magnetic field available to magnetize the fastening bit and in turn magnetically retain a fastener. It is desirable to have a drive guide with better performance with an impact driver.